The invention relates generally to wind turbines and more specifically to structures for enhancing installation and maintenance activities related to wind turbines.
Wind turbine towers are large structures, sometimes extending to significant heights to accommodate large wind turbine rotor blades and to strategically place the rotor blades within a wind path. For example, a typical tower may have a height as high as about 100 meters (m). Such a tower may include multiple sections, often a bottom, a middle and a top section. The length and number of individual sections may vary according to the application and height of the structure. At various heights of the wind turbine tower, landings are provided. The landings include openings for ladders to allow operators and maintenance personnel to climb between landings. The landings may also include openings above each other to allow small components, tools and equipment to be lifted from a base of the wind turbine tower to a top landing of the tower.
Mounted on top of the support tower for wind turbines is a nacelle. The nacelle houses, or encloses, the equipment and components of the wind turbine and includes hubs for the wind turbine blades and the power train including the bearing, gearbox and electrical generator for the wind turbine.
FIG. 1 illustrates an exemplary wind turbine tower. Nacelle 102 is mounted atop a tall tower 104, only a portion of which is shown in FIG. 1. Wind turbine 100 also comprises a rotor 106 that includes one or more rotor blades 108 attached to a rotating hub 110. Although the wind turbine 100, as illustrated includes three rotor blades 108, there are no specific limits on the number of rotor blades. The rotating hub 110 may include an access hatch 107 at a forward end.
FIG. 2 illustrates an exemplary internal arrangement for various components housed in nacelle 102. In some configurations, one or more microcontrollers within control panel 112 comprise a control system used for overall system monitoring and control. In some configurations, a variable blade pitch drive 114 is provided to control the pitch of blades 108 (not shown in FIG. 2) that rotor hub 110 as a result of wind. In some configurations, the pitch angles of blades 108 are individually controlled by blade pitch drive 114. Rotor blades attach to the hub on inner flange of a rotating race for rotor blade bearing. A stationary race for the rotor blade bearing is mounted to the hub. Rotor hub 110 and blades 108 together comprise wind turbine rotor 106. A spinner-assembly 105, shaped like a nose cone, may cover the exterior of the hub, including spaces between rotor blades. Access hatch 107 may be provided at the forward end of rotor hub 110. At least one access port 135 may be provided to the internal spaces of spinner assembly 105. At least one rail or ladder 136 may be provided for crossing an outer surface of the spinner assembly to the access port 135. Lifting ears 160 for the rotor hub 110 may be provided.
FIG. 3 illustrates a perspective view of a rotor blade bearing flange of the rotor hub with a removed blade. The pitch drive 114, which is firmly fixed to rotor hub 110, is mounted inside the rotor hub. Drive element 130 of pitch drive 114 is a gear wheel, which interacts with the inner gear rim of flange 132. Flange 132 may be firmly attached to a rotor blade and is rotatably located within rotor hub 110 (attached to the rotating race for the rotor blade bearing). Thus, pitch drive 114 enables a swiveling movement of its corresponding rotor blade, whereby the swivel axis of the rotor blade is roughly parallel to the longitudinal axis of the blade. Outer flange 134 may hold stationary race for the rotor blade bearing and is bolted with a plurality of peripheral bolts 111 to the rotor hub 110.
The bolts 111 holding outer flange 134 may currently also serve for mounting of lifting ears 160 in place on the hub 110. As mounted, the lifting ears 160 may project generally radially from the hub 110, and circumferentially with respect to the outer flange 134 of the rotor blade bearing, such that lifting ears on adjacent rotor blade bearing outer flanges 134 line up. A plurality of holes 165 may be provided in the lifting pads 160 for lifting slings to enable lowering and hoisting of the hub 110 to its operating position on the tower.
While such dedicated lifting pads are functional for hub lifts, each lifting pad may weigh about 300 lbs and is expensive for the this limited function. Further, unnecessary weight at the top of a 100 meter tower is undesirable.
Again referring to FIG. 2, the wind turbine includes a main rotor shaft 116 connected to hub 110 via main bearing 119. Gearbox 118 drives a high-speed shaft of generator 120. In other configurations, main rotor shaft 116 is coupled directly to generator 120. The high-speed shaft (not identified in FIG. 2) is used to drive generator 120, which is mounted on mainframe 117. In some configurations, rotor torque is transmitted via coupling 122.
FIG. 4 illustrates a spinner assembly 105 for a wind turbine hub in greater detail. A strong, but lightweight exterior covering of fiberglass or the like is provided to form a front nose section 151 with three extensions 152 formed to the rear. The rear directed extensions 152 may cover the hub area between the rotor blades. Each extension may be mounted to an exterior surface on the hub with multiple struts 153, thereby providing support for the entire spinner assembly. The spinner assembly 105 may provide for three access ports 135, one between the nose section 151 and each extension piece 152. The exterior surface of the spinner extension may include a fiberglass rail or a fiberglass ladder 136 with rungs for the operator to climb on. When the hub is aligned such that any of the three access ports is on top, a worker may climb over the hub, using the rail or ladder 136 and enter the spinner assembly 105 through the access port using the associated ladder 136. Once inside the spinner assembly, the worker may use a ladder complex 138 to move about to get to a front hatch 107 of the huh, from which entrance to the hub is possible.
FIG. 5 illustrates an isometric view of a typical hub arrangement with the spinner assembly removed. Front hatch 107 is opened to gain access to the interior of the hub 110.
While the spinner assembly provides a nose cone and entry scheme to the front hatch of the hub, it is an expensive component and it is not required for a streamlined wind flow around the nacelle. At the same time, the access route between the nacelle and the access ports into the spinner may provide limited gripping points for a worker traversing the route, while at a height of over 100 meters from the ground.
Accordingly, there is a need to provide a safe and effective way for operators to gain entry to the hub, without requiring major changes to the hub structure.